STEAP4 belongs to the STEAP (six transmembrane epithelial antigen of prostate) family, and resides in the golgi apparatus. It functions as a metalloreductase that has the ability to reduce both Fe(3+) to Fe(2+) and Cu(2+) to Cu(1+),using NAD(+) as acceptor. Studies in mice and human suggest that this gene maybe involved in adipocyte development and metabolism, and may contribute to the normal biology of the prostate cell, as well as prostate cancer progression. Alternatively spliced transcript variants encoding different isoforms have been found for this gene. Recombinant human STEAP4 protein, fused to His-tag at N-terminus, was expressed in E.coli.